You just unboxed a shiny new brake rotor, and it feels slightly oily or greasy to the touch. That is not a defect - it is a protective coating, and it absolutely must come off before you install the rotor. Skip this step and you invite poor braking and noise. Here is why and how.
Why new rotors are oily
Bare cast iron rusts fast (see why rotors rust overnight), so manufacturers coat new rotors in a protective oil or wax film for shipping and storage. It keeps the friction surfaces from rusting on the shelf. But that same film is the enemy of braking - oil between the pad and rotor drastically reduces friction.
What happens if you skip cleaning
- Weak braking until the coating burns off unevenly.
- Glazing and noise as the oil bakes onto the surface.
- Uneven bedding of the new pads, which can cause a pulsing pedal - see bedding guide.
- Contaminated pads in the worst case, which may then need replacing.
How to clean new rotors
- Spray the entire rotor - both friction faces especially - with a quality brake cleaner (brake parts cleaner or a similar solvent).
- Wipe with a clean, lint-free cloth.
- Repeat until the cloth comes away clean and the surface is dry and grease-free.
- Handle the cleaned rotor by the edges or hat to avoid fingerprints - skin oil counts too.
The same care for pads and hardware
Keep grease off the friction surfaces of the pads and rotor - grease belongs only on slide pins and contact points, never the braking surface. See where to apply brake grease. Then bed the new pads in properly. Start with quality pads and rotors for your vehicle, and fit fresh hardware. A five-minute cleaning makes the difference between quiet, strong brakes and a squealing, weak install.